Commercial depilatories presently on the market have many negative attributes. One of the worst is the malodor given off by those based on alkaline thioglycolate. Other disadvantages of present depilatory systems include their general messiness and the lengthy processing time which contributes to dermal irritation problems in some users.
The use of essentially odorless, soluble alkali stannite systems as depilatories has been known for some time. However, these systems have suffered from the disadvantage that soluble stannite rapidly decomposes to stannate, Sn(IV) and metallic tin, Sn(O), or reacts in the presence of water to form stannous oxide and alkali metal hydroxide, unless it is stabilized in some manner. Attempts to stabilize stannites utilizing either soluble silicates or certain organic compounds having three or more hydroxyl groups are described in Stoddard and Berlin, U.S. Pat. Nos. 2,123,214, and 2,199,249. These systems suffer from the fact that when stannites are used at pH 12.6 or less, the amount of time required to obtain complete depilation is increased, consequently increasing the possibility of dermal irritation.
We have found that aqueous alkali stannite systems are effectively stabilized by the addition of polyhydroxycarboxylate anions having five to seven carbon atoms and four to six hydroxyl groups. The resulting soluble stannite/acid complex depilates rapidly and effectively in the pH range from 12.8 to 13.3 with substantially no irritation.